display model pk entries (#851)

lib/widget/stock/location_display.dart

@@ -366,6 +366,7 @@ class _LocationDisplayState extends RefreshableState<LocationDisplayWidget> {
 
     List<Widget> tiles = [
       locationDescriptionCard(),
+      if (showPk && location != null) pkTile(location!.pk),
       Expanded(
         child: PaginatedStockLocationList(filters, title: L10().sublocations),
         flex: 10,

lib/widget/stock/stock_detail.dart

@@ -525,6 +525,10 @@ class _StockItemDisplayState extends RefreshableState<StockDetailWidget> {
       return tiles;
     }
 
+    if (showPk) {
+      tiles.add(pkTile(widget.item.pk));
+    }
+
     // Location information
     if ((widget.item.locationId > 0) && (widget.item.locationName.isNotEmpty)) {
       tiles.add(